A shuttle complex has been proposed for libraries in which a plurality of library strings connecting a plurality of libraries with storage media such as tapes are arranged in rows, and the library strings are connected by shuttle connections. This shuttle complex is already in practical use (IBM System Storage TS3500, etc.). In this shuttle complex, cars able to move within a shuttle connection move cartridges including storage media such as tapes between library strings, and the cartridges are mounted in a drive or stored in a slot within the library frame specified as the destination point.
In methods of the prior art for moving cartridges between library strings, when there is no car in the library string at the departure point, an available (empty) car has to be moved from the closest library string before the cartridge can be loaded into the car and moved to the library string at the destination point.
However, in the moving methods of the prior art, when there is no car in the library string at the departure point, an empty car not carrying a cartridge has to be moved beforehand to the library string at the departure point. Therefore, the time required to move cartridges between library strings is extended to include the movement of empty cars, and the amount of time required to move empty cars increases as both the traveling distances of cartridges and the number of traveling runs increases.